Develop an effective, safe, and clinically applicable imaging method for the localization and sizing of myocardial infarction using antimyosin antibody. Development of an antibody to first canine and later human myocardium. Preparation and purification of antibodies Fab fragments for scanning studies. Perform experiments using double labeling employing I-125 myosin specific antibody and I-131 normal immunoglobin. Perform scanning studies in a canine model of acute myocardial infarction. Evaluate the role of tagged myosin antibody for imaging myocardial infarction in man.